FEM simulation of welded joint geometry influence on fatigue crack growth resistance

Abstract

Fatigue behaviour of welded joints is investigated, in terms of welded joint geometry and the fatigue crack position. It is based on previous work which involved numerical simulation of fatigue crack growth in a welded joint made of micro-alloyed, low-carbon pressure vessel steel P460NL1, with the main focus on fatigue crack growth rate through different welded joint regions. The goal here was to change the size of the heat affected zone, as the region in which the fatigue crack initiated, and to compare the results obtained for new crack length values with the original ones, obtained by creating numerical models based on experimental data. A number of models were created, some of which simulated the case with a bigger heat affected zone (and, consequently, a smaller crack length in the weld metal), and other which simulated the case with a smaller heat affected zone. Due to the micro-structural differences between these two welded joint regions, noticeable differences appeared in the numbers of cycles obtained for each zone with varying fatigue crack lengths, as well as in the total number of cycles for both zones through which the crack propagated.